The University of the Highlands and Islands is working on The Cairns Project along with others, including the organisation Orkneyjar.

Scraps from humans

Site director Martin Carruthers said the coprolites were not the most photogenic of the discoveries, but added that they were still an important find.

He said: "They tend to lose their integrity quite easily when they're just a couple of thousand years old rather than petrified as stony fossils if they're a great deal older.

"These are probably from medium-sized mammals like a cat or dog and their significance is two-fold.

"They tell us something of the conditions prevailing inside the broch during its use, at least towards the end of its use, in that there were animals probably feeding off the waste products of human food, as well as probably keeping numbers of vermin lower as well.

"The other useful thing about these coprolites is that their contents may well give good additional proxy information on the foodstuffs present in the broch as these animals will probably be eating scraps from the human diet."

Image copyrightThe CairnsImage caption
Whale and other animal bones have already been found at the site